Bndwidth Control Wrt54g

I have 3 WRT54Gs and 1 WAP54g serving Internet at long range (4 km total) I have 6 wireless clients at different spots. I use DD-WRT pre5 Talismen (it's great) and Freya for the WAP54g. I put 1PC at the Internet gate to control the bandwidth and I want to pass it using some modules for the firmware to control the bandwidth in exact manner. 10 KB each user p.ex. no more or less, exact value each.

here's what i'd do, there may be a way to do this right on the router, i've never tried nor do I run that firmware...
you say you already have a PC between the last hop and the internet, i'd setup bandwidth limitation on that and allocate a block of IPs to each AP and have the AP filter out any other ips that shouldn't be used on that AP...